Stereoselective synthesis of 3-alkylideneoxindoles by palladium-catalyzed cyclization reaction of 2-(alkynyl)aryl isocyanates with organoboron reagents.

A palladium(0)/monophosphine catalyst promotes a cyclization reaction of 2-(alkynyl)aryl isocyanates with organoboron reagents to produce stereodefined 3-alkylideneoxindoles. The alkynyl and isocyanato groups undergo oxidative cyclization with Pd(0) to form an oxapalladacycle intermediate. Subsequent transmetalation and reductive elimination afford the product.